As a Eurasian from Singapore, I have to say that there is no one authentic recipe, and each Eurasian household will claim that theirs is the original. "Devil Curry" is not the actual name, but "Curry Debal."
It originally was not cooked on Christmas, but after Christmas, with all the leftover meats. It is not supposed to be super spicy; over the years it was assumed to be hot because of the redness of the gravy (and once the name "Devil" was coined).
There are at least 10 different recipes which I know of here in Singapore and Malaysia.

Reviewer:

I must have done something wrong. The curry smelled fantastic, but the flavor was just not there only the heat. I believe I will not attempt this recipe again. :( I could not eat it and my boyfriend was able to shove it down, but I was very unhappy with it.

Reviewer:

The curry was nice and spicy, and turned out OK. As was mentioned before, making a paste from all those ingredients was pretty tough!
6 red onions seems like a lot. Allspice is not mentioned in the commontary, but galangal is, so maybe the ingredient list is supposed to read 1 tsp galangal? And how much shrimp paste to use? I used about 1 Tbsp, but I think it could have used more.
The dried chilies are spicy! I used only about 15 and that was quite good enough for me!

Reviewer:

Finding the ingredients was reasonably easy. Galangal sounded important. I was determined to find it. A local Chinese supermarket offered both chopped preserved in a jar and fresh ones. I opted for fresh. I was less lucky with the candlenuts so I substituted Brazil Nuts as suggested by an ingredients substitution website. Finally, I used fresh birds eye green chile, having watching something similar being prepared while in Asia.
The volume of ingredients to blend was a major effort and my poor blender was in melt down failing to make anything like a paste. Fresh Galangal is quite hard and with the nuts it is just too much. I aborted and removed and grated the Galangal and nuts by hand then back for a finish off blend. Also, the quantity of Ginger and Galangal are not listed in the ingredients – I used a couple of bulbs of each. I think if you like it then just add more.
Beyond that, it was really simple. Cooling times and liquid exactly as expected and results good